Torpedo signal for railways



May 9, 1950 w. R. GRACEY, JR

TORPEDO SIGNAL FOR RAILWAYS 5 Sheets-Sheet 1 Filed Feb. 28, 1948 INVENTOR. i2 1?. Gravy/n Hi5 ATTORNEY May 9, 1950 w. R. GRACEY, JR

TORPEDO SIGNAL FOR RAILWAYS 3 Sheets-Sheet 2 Filed Feb. 28, 1948' mzlmm 2, 5%?

Patented May 9, 1950 roarsno SIGNAL FOR RAILWAYS William It. Gracey, .l'r., Swissvale, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application February 28, 1948, Serial No. 11,992

12 Claims.

My invention relates to torpedo signals for railways, and particularly to improvements in torpedo signals of the type described in Letters Patent of the United States No. 2,362,347, granted to Herbert L. Bone and Kenneth J. J. McGowan on November 7, 1944.

Torpedo signals of the type referred to are generally used in conjunction with a fixed wayside visual signal at railroad intersections, drawbridges, or the like, and they serve as a means to provide a supplemental audible warning to an engineman in the event that he overruns the visual signal while it is in its stop position. They also provide a means of identifying promptly an engineman who overruns such a signal, so that disciplinary measures may be taken.

In the aforesaid Patent No. 2,362,347, there is shown a torpedo signal adapted for mounting alongside a track rail. A motor is provided for moving the machine between a clear position and a firing position. In the firing position, the cover of the machine projects above the track rail so that it will be engaged by the wheel of a passing vehicle. The cover is supported by a firing pin, which is in turn supported at such times by a torpedo set in place under the firing pin by the machine as it moves to its firing position. When the machine is moved to its clear position, the torpedo is withdrawn from under the firing pin, and the cover is lowered so that it will not be engaged by any wheel passing on the track. A signal is provided which responds to the cover position, and indicates to the tower operator either that a torpedo has been exploded or that the machine is in firing position with no torpedo under the firing pin.

Since torpedo machines of the type described are used to inform an engineman that he is approaching a dangerous location, it is important that the firing of the torpedo be con sistent and reliable. It has been found difiicult to obtain torpedoes which will fire consistently when run over at slow speeds, whether they are placed on a rail or used in a signal machine,

It is also desirable that such a machine be so constructed that it cannot be operated in an unauthorized manner, for example, by being stepped on.

It is therefore an object of my invention to provide a torpedo signal machine for railways, in which the torpedo is exploded by a firing pin driven against the torpedo with an impact or hammer action which is completely independent of the speed with which a vehicle passes over the machine.

Another object is to provide a torpedo signal 2 machine in which the torpedo will not be exploded unless the load on the treadle of the torpedo machine exceeds a predetermined value greater than the weight of the average man.

Another object is to provide a torpedo signal machine in which the torpedo will be completely unstressed up to the moment of firing.

A further object is to provide an improved electrical signal means for use in connection with such a machine to give separate indications of the passing of a vehicle over the machine and of the fact that the magazine in the machine is emptied.

A further object is to accomplish these results, using so far as possible, the parts of the existing torpedo machine shown in the patent to Bone et al. No. 2,362,347.

I accomplish these results in the torpedo signal described herein by providing in the bottom of the cover which serves as a treadle, a downwardly directed barrel to receive the firing pin. A spring in the barrel biases the firing pin downwardly. The firing pin is provided with a trigger or latch mechanism by which it is supported on the torpedo slide when the machine is in its firing position. At this time the pin is spaced from the torpedo so that the torpedo is unstressed. When the load on the treadle exceeds a value, say for example, 250 pounds, which is determined by the strength of the spring in the barrel and the distance through which the cover must be depressed, then the lower end of the barrel moves down over the pin far enough to engage and release the trigger so that the pin is then moved downwardly against the torpedo by the biasing spring. When the machine is moved to its firing position, the treadle is raised to its firing position, whether there is a torpedo in the machine or not. A signal controlled by the cover of the machine indicates whenever the cover has been depressed by a vehicle, whether or not a torpedo was fired at that time. An additional signal is provided to indicate when the torpedo magazine is emptied.

Other objects and advantages of my invention will become apparent as the description proceeds.

I shall describe one form of torpedo signal ems bodyin my invention, and shall then point out the novel features thereof in claims,

In the accompanying drawings, Fig. 1 is a plan view showing a torpedo signal embodying my invention applied to a railway track rail together with auxiliary apparatus commonly used in connection with such a signal. Fig. 2 is an elevation, partly in cross section, showing a torpedo signa1 embodying my invention, with the parts in their clear position. Fig. 3 is a view similar to Fig. 2, with the parts in their firing Position. Fig. 4 is a cross sectional view taken along the lines IVIV of Fig. 3. Fig. 5 is a Vie similar to Fig. 4, with the parts in the position they assume when the device is just ready to fire a torpedo. Fig. 6 is a view similar to Figs. 4 and 5, with the parts in their positions after a torpedo has been fired. Fig. 7 is a fragmentary view, somewhat diagrammatic, showing a circuit controller operated in response to the condition of the torpedo magazine and. a wiring diagram of a signal circuit operated by that circuit controller. Fig. 8 is a side elevational view of a fragment of the torpedo signal, showing another electrical circuit controller used in connection therewith, and having the cover removed and a part of the casin broken away to better illustrate the construction of some of the parts. Fig. 9 is a wiring diagram showing a control circuit suitable for operation by the controller of Fig. 8. Fig. 10 is a fragmentary view similar to Fig. 3 with some of the parts omitted, to show the details of the cams and cam lugs which move the cover under certain conditions.

Referring to Fig. 1, the torpedo signal is generally indicated at I, and is mounted on the outer side of a track rail 2, b means of rail clamps 3 and hook bolts 4, so that the torpedo signal machine I lies between a pair of adjacent crossties 5.

The signal machine I is moved between its clear and firing positions by means of a fluid pressure motor 6 connected to the signal machine I through an adjustable screw jaw I and a link 8.

The fluid pressure motor forms no part of my present invention, and is of conventional construction, being provided with ports at both ends of the cylinder so that it is double acting. The supply of fluid pressure to the motor is controlled by a suitable valve mechanism V also of standard construction, including a normal electromagnet N efiective when energized to admit fluid to the right-hand end of the motor to thereby move the piston rod out of the cylinder to its projected position and thus operate the torpedo signal machine I from its clear to its firing position. A reverse electromagnet R is effective when energized to admit fluid to the opposite end of the cylinder to move the piston rod into the cylinder to its retracted position and thus operate the torpedo signal machine I from its firing position to its clear position.

Associated with the motor 6 is a circuit controller 9, which may for example be similar to that described and claimed in Letters Patent of the United States No. 2,190,520, granted February 13, 1940, to Edwin G. Little. This circuit controller is provided with an operating shaft I0 connected by a crank II to the motor I5, and includes a plurality of contacts each controlled by a different cam, the cams being individually adjustable to enable the contacts to become open or closed at any desired point in the stroke of the motor. These contacts may be used to control visible signals for indicating the condition of the torpedo signal I in a manner which will be described hereinafter. The wires leading to and from the circuit controller 9 are carried through a conduit I2 to a junction box I3, which latter is also connected with a parkway cable I4 and also with another conduit I5 leading to the valve mechanism V.

The torpedo signa1 machine I is provided with 4 another circuit controller generally indicated at E6 in Fig. 1 and shown in detail in Fig. 8. This controller is connected through a conduit I1 with the circuit controller 9.

The torpedo signal machine I is generally similar to that completely described in the Bone and McGowan Patent No. 2,362,347, and reference is made to that patent for a complete description of certain parts of the unit which are not considered essential to the present invention and are therefore not described in detail herein.

Referring to Fig. 2, it may be seen that the torpedo machine unit includes an anvil base I8, an anvil I9 slidable along the upper surface of the anvil base I8, and a torpedo slide 20 slidable along the upper surface of the anvil I9. The torpedo slide 20 is connected to the link 8, which as mentioned in connection with Fig. l, is driven by the motor 5. The torpedo slide 20 is provided with an aperture 2% adjacent its left end, as it appears in Fig. 2, to receive a torpedo 2I. The torpedo slide is connected with the anvil I9 by a lost motion connection comprising a vertical pin 22 (see Fig. 3) extending through an opening in the anvil and provided at its upper end with a head 22a disposed in a longitudinal slot 20b formed in the underside of the slide 20. The parts are so proportioned that when the slide is moved to its clear position, as shown in Fig, 2, the left end of the slot 20?) engages the head 22a. of the pin 22 and acts through the pin to move the firing anvil away from the rail to the position shown in Fig. 2.

A cover 23 for the torpedo signa1 machine I is pivotally mounted at one end on a shaft 24 carried by main body 25 of the torpedo signal I. The end of cover 23 nearest the rail 2 is provided with a flat surface 23a which serves as a treadle to be engaged by the wheels of vehicles passing b on the rail. A barrel 23b is integrally formed in the underside of cover 23 near its left end. A firing pin 26 is received in the barrel 23b, and is biased downwardly in the barrel by a sprin 21. A stop pin 28 extends through the firin pin 26 and through a slot 23c in the barrel 23b, so as to limit the downward movement of the firing pin in the barrel.

Near its lower end, the firing pin 26 is provided with a pair of diametrically opposite recesses 26:: (see Fig. 4) which are connected at their upper ends by a transverse bore 26b. A pair of generally L-shaped triggers or latches 29 are disposed in the recesses Zea. A spring 30 is received in the bore 26b, and biases both triggers 29 for movement outwardly of the pin 25. Each trigger 29 carries a pin 29a, which moves in a slot 260 in the pin 26, so as to limit the outward movement of the triggers 29.

When the torpedo slide 20 is in the position shown in Fig. 2, the aperture 20a is aligned with a generally cylindrical magazine 30, which holds a quantity of torpedoes 2|. The stack of torpedoes 2I is held down by a follower 3|, loaded by a spring 32, whose opposite end is held in place by a cap 33 on the magazine 30.

The cover 23 is provided with a downwardly depending cam 34, which cooperates with an upwardly projecting cam lug 35 on one side of the slide 20. A similar cam and cooperating cam lug are provided on the opposite side of cover 23 and slide 20.

Operation When the parts are in the position shown in Fig. 2, the treadle portion 23a of cover 23 is lowered below the top of rail 2 suiiiciently far so that it will not be engaged by a wheel on a passing vehicle, even though the wheel may have become channelled through long wear.

With the parts in the position shown in Fig. 2, let it now be assumed that the motor .5 is operated to change the torpedo signal to its firing position, which position is illustrated in Fig. 3. The motor moves link 8 and slide 2%] to the left, carrying with it the lowest of the torpedoes 2!. of anvil it until the head 22a of pin 22 engages the right end of recess 2%. At this time the relative positions of the slide and anvil are as shown in Fig. 3. Thereafter, the slide and anvil move together until they reach the position shown in Fig. 3, wherein the torpedo El is under but spaced from the firing pin it. During the movement of the slide 2% from its clear position to its firing position, the cam lugs 35 engage the cams 34 on the cover and iift them, thereby lifting the cover 23, which carries with it he firing pin 26, thereby moving the firing pin out of the path of the anvil i9 and the torpedo slide 26. As the slide reaches the firing position shown in Fig. 3, the cams lower the cover 23 again until the triggers 29 rest on the slide (see Fig. 4).

It should be observed that with the triggers resting on the slide 29, the cover is supported by spring 21, firing pin 26 and the triggers 29. If, now, a wheel of a vehicle passing on the rail 2 engages the cover 23 and depresses it, the spring 2'! is compressed. The pin 26 is held up by the triggers 29, however, until the cover 23 moves downwardly far enough so that the lower end oi barrel 23b engages the outer surface of the triggers 29a, thereby forcing them inwardly in the pin 25 (see Fig. 5). As soon as the triggers 29 are pushed inwardly so that they no longer rest on the slide it, the pin 26 due to the release of the energy stored in the compressed spring 2'. moves rapidly downward, engaging the torpedo 2| and firing it.

The downward force on the cover necessary to compress spring 2? far enough to trip the triggers 25 is determined by the rate of spring 2i and by the distance through which the lower end of the barrel: 2% must travel before it moves the triggers 29. to their released position. This distance and the rate of spring 2'! are preferably so chosen that the triggers it cannot be tripped by a person of normal weight stepping on the cover 23. For example, these factors may be chosen so that the torpedo will not he exploded unless the weight on the cover exceeds 259 pounds.

After the torpedo is exploded, the parts have the positions shown in Fig. 6. It may be seen that in this position again the cover is supported by the spring 21. If the cover is overrun by succeeding wheels on the Vehicle which fired the torpedo, it is depressed against the spring 2'! and none of the parts are unduly stressed.

After a torpedo has been exploded, the mechanism may be reset for a new operation by actuating the motor 6 to retract the slide 29 to the position it occupies in Fig. 2. During this movement of the slide, the cams 535 lift the came as and the cover 2-3. As the cover 23 moves up- The slide 26 moves along the upper surface wardly, the lower ends of the slots 23c engage the stop pin 28,

thereby carrying firing pin 25 tion of the signal, they will again perform their function as previously described.

Fig. 7 illustrates a signaling arrangement for indicating when the torpedo magazine 30 is emptied. As there shown, the follower 3| carries a contact actuator em, which projects through a slot 30a in the side of the magazine 30. A. pair of electrical contacts 33 and 31 are mounted on an insulating support 38 and connected to terminals 39 and 49, respectively. The contact 36 is stationary, and self-biased to engage the movable contact 31, which projects into the path of the actuator dict. These contacts are normally closed, and it may be seen that when the last torpedo is removed from the magazine the actuator 31a engages the contact 31 and moves it away from contact 36. The contacts and 3'! are connected in a normally closed relay circuit including a battery 4| and a relay 12. An electrical signal lamp 43 is provided, energized by means of a battery 44 through a circuit including a back contact 45 of relay 42. When the magazine is emptied, the contacts 35 and 3's are opened, deenergizing relay s2 and allowing the back contact 45 to close, thereby completing an energizing circuit for signal lamp 43. Although I have illustrated a visual signal, it will be readily understood that an audible or other sensible signal may be used in its place. The signal lamp @3 is usually located in an adjacent tower or other location to inform an operator that the supply of to!- pedoes in the torpedo signal machine should be replenished.

It is desirable to be able to indicate at a remote point, such as an interlocking tower, when a train fires a torpedo, to enable the particular train which operated the signal to be identified. For this purpose I have provided the signal with a contact mechanism which is intended to be used in conjunction with one of the contacts of the circuit controller 9 as will be made clear presently.

This contact mechanism is arranged to be bolted to the side of the main body casting 25, and is designated as a whole by the reference character It. As best seen in Fig. 8 this circuit controller comprises an auxiliary housing 46 closed by a removable cover M. Disposed within the housing is is a fixed contact finger t8 and a cooperating movable contact finger :39 secured respectively to contact supports 5? and 5!. The supports 59 and 5! are insulated from the housing 46, but are electrically connected with terminal posts 52 and 53, whereby external electrical connections with the contact fingers may be readily made. The movable finger 49 is provided at its upper end with a curved actuating member tea which cooperates with an insulating contact operating cam 54 secured to the lower end of an operating plunger 55. The plunger 55 is slidaxbly mounted in bushings 55 disposed in a vertical opening 5i formed in the housing 36, and is constantly biased to an upper position by means of a compressed coil spring 5% disposed in the housing as between the cam 54 and a plug 59 which closes the lower end of the opening 5'5. The upper end of the plunger 55 cooperates with a screw adjustably mounted on a lateral extension 6! formed on the cover. The extension 6! serves to protect the contact mechanism from ice and snow, and includes an annular portion Bla which surrounds the upper end of a tubular portion of the housing as through which tubular portion the upper end of the plunger 55 extends. As shown the parts are so arranged that when the plunger 55 is moved to its upper position by the spring 58, the cam 54 engages the curved end 49a of the movable finger 49 and forces it into engagement with the fixed finger 48 to close the contact 48-49. The screw 60 is so adjusted that when the cover is in its ready to fire position with the firing pin 26 above a torpedo, the screw 69 engages the upper end of the plunger and depresses it slightly but not enough to open the contact. It will be obvious, therefore, that when a torpedo is fired, the downward movement of the cover which caused the torpedo to be fired acts through the screw 69 to degress the plunger and when this happens, the cam 54 moves out of engagement with the contact finger 49. The finger 49 is biased by its own resiliency to a position in which it is out of engagement with the fixed finger 48, and it follows that the movement of the cover to its lowermost position causes the contact 49-48 to open.

It should be made clear that while the contact 49-46 is arranged as a normally closed contact, this contact could equally well be arranged as a normally open contact as is obvious.

Inasmuch as the cover 23 is free to move to its lowermost position both when a torpedo becomes fired and when the slide 20 is moved to its clear position, it is necessary in order to distinguish between the clear and fired positions of the torpedo machine to employ a contact of the circuit controller 9 in conjunction with the contact 48-49 to provide an indication at a remote point of the firing of a torpedo. One circuit arrange ment for accomplishing this result is shown in Fig. 9 wherein the contact of the circuit controller 9 is designated 62-63 and is so adjusted that this contact is closed when the torpedo slide is in the clear position and remains closed when the slide is moved toward the firing position until after the cooperating cam lugs 34 and 35 have lifted the cover 23 to its upper position. The contacts 48-49 and 62-63 are connected in parallel in a pick-up and a stick circuit for an indication relay R. The pick-up circuit also includes a push button P and passes from a suitable source of current here shown as a battery X through wires 64 and 65, the contacts 48-49 and 62-63 in parallel, wires 66 and 6?, push button P, and the winding of relay R back to battery X. When this circuit becomes closed, relay R picks up and closes its stick circuit which passes from battery X through wires 64 and 65, the contacts 62-63 and 48-49 in multiple, wire 66, front contact 68 of relay R, and the winding of relay R back to battery X. Once the stick circuit for relay R becomes closed, relay R remains energized until the contacts 62-63 and 48-49 both become simultaneously opened. This hapa becomes lighted to give a visible indication that i a torpedo has been fired, and buzzer E operates to give an audible indication. The lamp L remains lighted and buzzer E continues to operate until one or the other or both of the contacts 62-63 or 48-49 become closed and push button P is operated while such contact or contacts are closed. To close contacts 62-63 it is necessary for the torpedo slide to be returned to its clear position.

From the foregoing, it should be apparent that I have provided a torpedo signal machine in which the torpedoes are unstressed until fired. Furthermore, a torpedo is fired only when the weight on the machine exceeds a predetermined minimum and the torpedo is fired by a hammer mechanism whose operation is independent of the speed at which the machine is run over by a moving vehicle. I have also provided for use with the machine independent signals which indicate respectively when the machine has been run over and when the torpedo magazine in the machine is empty.

Although I have herein shown and described only one form of torpedo signal for railways embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. A torpedo signal, comprising a casing adapted for mounting adjacent a track rail, a torpedo in the casing, a firing pin in the casing, a torpedo slide apertured to receive the torpedo and movable between an active position wherein the torpedo is aligned with the firing pin and a retracted position wherein the torpedo is out of the path of the firing pin, a treadle on said casing movable between an active position where it will be engaged by a vehicle wheel passing over the track and a retracted position where it will not be so engaged, means movable concurrently with the torpedo slide for moving the treadle to its active position as the torpedo is moved to its active position, means for supporting the treadle in its active position including said pin, a spring between the treadle and the pin, trigger means for supporting the pin on the torpedo slide in a position spaced from the torpedo, and means efiective when the treadle and spring are deflected by a vehicle wheel to release said trigger means so that the pin is moved by the spring to fire the torpedo, said slide being effective when retracting the torpedo to move out of its supporting relation to the trigger means, thereby permitting the trigger means, pin, and spring and treadle to move together as the treadle moves to its retracted position.

2. A torpedo signal, comprising a casing adapted for mounting adjacent a track rail, a torpedo in the casing, a firing pin in the casing, a torpedo slide apertured to receive the torpedo and movable between an active position wherein the torpedo is aligned with the firing pin and a retracted position wherein the torpedo is out of the path of the firing pin, a treadle on said casing movable between an active position where it will be engaged by a vehicle wheel passing over the track and a retracted position where it will not be so engaged, means movable concurrently with the torpedo slide for moving the treadle to its active position as the torpedo is moved to its active position, a spring biasing the pin for movement in a direction to fire the torpedo, trigger means for supporting the pin on the torpedo slide in a position spaced from the torpedo, and means efiective when the treadle is deflected by a vehicle wheel to release said trigger means so that the pin is moved by the spring to fire the torpedo.

3. A torpedo signal, comprising a casing adapted for mounting adjacent a track rail, a torpedo in the casing, a firing pin in the casing, a torpedo slide apertured to receive the torpedo and movable between an active position wherein the torpedo is aligned with the firing pin and a retracted position wherein the torpedo is out of the path of the firing pin, a treadle on said casing movable between an active position where it will be engaged by a vehicle wheel passing over the track and a retracted position where it will not be so engaged, means movable concurrently with the torpedo slide for moving the treadle to its active position as the torpedo is moved to its active position, a barrel attached to the treadle and extending downwardly therefrom to guide the pin, a spring in the barrel biasing the pin for movement in a direction to fire the torpedo, and trigger means for supporting the pin on the torpedo slide in a position spaced from the torpedo, the end of said barrel being effective when the treadle is deflected by a vehicle wheel to release said trigger means so that the pin is moved by the spring to fire the torpedo.

4. A torpedo signal, comprising a casing adapted for mounting adjacent a track rail, a treadle on said casing movable between an active position wherein it is engageable by the wheel of a vehicle passing over the rail and a retracted position where it cannot be engaged by such a wheel, a barrel attached to the underside of the treadle and extending downward therefrom, a firing pin in the barrel, a spring in the barrel between the treadle and the pin and biasing the pin downwardly, said pin having a lateral recess therein, a trigger in said recess, spring means biasing the trigger outwardly of the pin, a trigger support having an aperture aligned with the pin and effective to limit downward movement of the pin as long as the trigger extends outwardly therefrom, means efiective when the treadle is depressed to engage the trigger and force it back into its recess so that the pin is then moved rapidly through the aperture by the spring, and a torpedo aligned with the aperture and fired by the pin when it passes through the aperture.

5. A torpedo signal as in claim 4, in which said pin has a pair of diametrically opposed latera] recesses therein and a transverse bore connecting said recesses in which a pair of triggers is provided one in each recess, and in which said spring means consists of a spring in said bore engaging both triggers and biasing them outwardly of their recesses.

6. A torpedo signal as in claim 4, in which the means for engaging the trigger and forcing it back into its recess is the end of the barrel.

'7. A torpedo signal as in claim 4, in which the torpedo is received in the aperture of the trigger support, and in which the trigger support is movable between an active position wherein the torpedo is aligned with the firing pin and a retracted position wherein the torpedo is out of the path of the firing pin.

8. A torpedo signal as in claim '7, including means movable concurrently with the trigger support for lifting the trigger ofi' the support during such movement.

9. A torpedo signal as in claim 8, in which the trigger lifting means includes cam means 10 for lifting the treadle, and stop means for limiting the movement of the pin out of the barrel.

10. Signal apparatus, comprising a casing adapted for mounting adjacent a track rail, a treadle on the casing movable between an active position where it will be engaged by a vehicle wheel passing over the rail and a retracted position where it will not be so engaged, means for moving said treadle between said positions, an explosive cartridge in the casing, a firing pin for engaging the cartridge to explode it, a spring retained in compression between the treadle and the pin, means for supporting the treadle in its active position including said pin, said spring and releasable latch means for holding the pin spaced from the cartridge, said latch means being released upon deflection of the treadle by a vehicle wheel and effective when released to allow the treadle to move to its inactive position and to allow the spring to forcibly move the pin into engagement with the cartridge, and means efiective upon restoration of the treadle to its active position to reset the latch means.

11. Signal apparatus, comprisin a casing adapted for mounting adjacent a track rail, a treadle on the casing movable between an active position Where it will be engaged by a vehicle wheel passing over the rail and a retracted position where it will not be so engaged, means for moving said treadle between said positions, a pin in the casing, a spring retained in compression between the treadle and the pin, means for supporting the treadle in its active position including said pin, said spring and releasable latch means for holdin the pin, said latch means being released by engagement of the treadle by a vehicle Wheel and effective when released to allow the pin to drop so that the treadle can move freely to its inactive position, signal means operated by movement of the treadle to its inactive position, and means effective upon restoration of the treadle to its active position to reset the latch means.

12. Signal apparatus, comprising a casing adapted for mounting adjacent a track rail, a treadle on the casing movable between an active position where it will be engaged by a vehicle wheel passing over the rail and a retracted position where it will not be so engaged, means for moving said treadle between said positions, an explosive cartridge in the casing, a firing pin for engaging the cartridge to explode it, a spring for driving the pin against the cartridge, releasable latch means for holding the pin spaced from the cartridge, said latch means being released by engagement of the treadle by a vehicle Wheel and effective when released to allow the spring to move the pin so as to fire the cartridge, and means eiTective upon restoration of the treadle to its active position to reset the latch means.

WILLIAM R. GRACEY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 341,553 Clark May 11, 1886 1,688,986 Ranzan Oct. 23, 1928 2,362,347 Bone Nov. 7, 1944 2,376,332 Adelman May 22, 1945 

